The blade roots are inserted into the recess through a window in a side wall of the recess, and they are then moved circumferentially along the recess so as to be held radially and axially relative to the axis of the wheel by means of co-operating shapes, the recess being of a cross-section that is in the shape of a dovetail or the like, and the blade roots having a shape that is complementary to that of the recess.
The blade roots are connected to the airfoils of the blades by platforms that, when the blades are mounted in the groove and juxtaposed circumferentially, surround the peripheral surface of the disk externally.
Manufacturing and assembly tolerances mean that the blade roots are received with clearance in the annular recess of the disk.
In operation, the blades are subjected to high levels of centrifugal force and they adopt a proper angular position relative to the axis of the rotor, in which position the radial clearance between the outer ends of the blades and an outer annular casing are minimized so as to improve the performance of the turbomachine.
An elastomer annular gasket is generally mounted in an annular groove in the peripheral surface of the disk, upstream and/or downstream of the blades, under the blade platforms, and having, in the free state, an outside diameter that is less than or equal to that of its mounting groove so as to avoid impeding the circumferential sliding of the blades in the annular recess of the disk.
In operation, the gasket expands radially outwards under the effect of centrifugal force and comes into contact with the blade platforms so as to damp blade vibration and/or to prevent air from passing between the platforms and the outer peripheral surface of the disk, since that would reduce the performance of the turbomachine.
When the turbomachine is at rest, and on starting, the blades of the wheel can tilt to a greater or lesser extent relative to their operating position, and their ends might rub against the outer casing, thereby deteriorating the blades and reducing the performance of the turbomachine.